1. Field of the Invention
The invention concerns a method for feeding and inserting weft yarns in a loom which includes a feed mechanism arranged to alternately feed at least two weft yarns supplied from at least two individual weft yarn feed devices, each feed device including a supply of yarn and means for selecting a weft yarn to be inserted into the fabric, the devices being driven by a control unit. The invention further concerns a feed mechanism to carry out the method.
2. Background of the Invention
Looms, and in particular gripper looms, are known in which the feed mechanism consists of a plurality of individual weft yarn feed devices each supplying the same type of weft yarn during consecutive insertions, the wefts being inserted by insertion means, for instance grippers, into a shed. The respective weft yarns from the individual feed devices remain joined to the lateral fabric edge between consecutive insertions, and are severed from the lateral fabric edge by insertion scissors at the beginning of the next weft insertion from the respective feed device. The junction to the lateral fabric edge is located in the vicinity of the first warp and, if the weaving includes a waste selvage, the junction is within the zone of the first waste warp yarn. In the event that the weaving excludes a waste selvage, the junction site is located in the vicinity of the lateral fabric edge. Insertion scissors for severing a weft yarn from its junction site at the beginning of the weft's insertion are known, for example from U.S. Pat. No. 3,621,885 or 4,964,442.
The known feed mechanism includes means to select the particular weft to be inserted by one of the insertion devices, the selection means being a yarn-presenting device in the case of a gripper loom which presents the particular weft to be inserted to the gripper, and one or more stop-motion devices to seize a ruptured weft. Each of the feed devices is equipped as a rule with a yarn supply made up of two bobbins, the end of the bobbin in use being connected to the beginning of a reserve bobbin. Typically, the feed mechanism also includes an accumulator unit between the weft yarn supplies and the presenting device. When weaving certain fabrics, for instance those for airbags or filters, the weft segments introduced into the fabric must be free of knots or other irregularities. When weaving this type of fabric, it is known to stop the loom using the stop motion upon detecting a knot or irregularity, such as occurs at the connection between bobbins, and to remove the weft with the irregularity. A danger is thereby incurred that during the ensuing startup, a so-called start-up strip will be created in the fabric, which is caused foremost by the wefts inserted immediately after startup not being beaten-up properly. Such start-up strips are especially undesirable in this type of airbag or filter fabric.